CN110539646A - Longitudinal speed estimation method and system for all-wheel-drive electric wheel automobile - Google Patents

Longitudinal speed estimation method and system for all-wheel-drive electric wheel automobile Download PDF

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Publication number
CN110539646A
CN110539646A CN201910721634.9A CN201910721634A CN110539646A CN 110539646 A CN110539646 A CN 110539646A CN 201910721634 A CN201910721634 A CN 201910721634A CN 110539646 A CN110539646 A CN 110539646A
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wheel
vehicle
longitudinal
formula
current moment
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Inventor
连小珉
陈浩
金达锋
袁良信
钱江
杜鹏
王源
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SUZHOU ZIJING QINGYUAN NEW ENERGY AUTOMOBILE TECHNOLOGY Co Ltd
Tsinghua University
Suzhou Automotive Research Institute of Tsinghua University
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SUZHOU ZIJING QINGYUAN NEW ENERGY AUTOMOBILE TECHNOLOGY Co Ltd
Tsinghua University
Suzhou Automotive Research Institute of Tsinghua University
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Priority to CN201910721634.9A priority Critical patent/CN110539646A/en
Publication of CN110539646A publication Critical patent/CN110539646A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2220/00—Electrical machine types; Structures or applications thereof
    • B60L2220/40—Electrical machine applications
    • B60L2220/42—Electrical machine applications with use of more than one motor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2220/00—Electrical machine types; Structures or applications thereof
    • B60L2220/40—Electrical machine applications
    • B60L2220/44—Wheel Hub motors, i.e. integrated in the wheel hub
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/46—Drive Train control parameters related to wheels
    • B60L2240/461—Speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/46—Drive Train control parameters related to wheels
    • B60L2240/465—Slip

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Electric Propulsion And Braking For Vehicles (AREA)

Abstract

The invention provides a longitudinal speed estimation method and system for an all-wheel-drive electric wheel automobile, and belongs to the field of vehicle dynamics control. The method is used for estimating the longitudinal speed of the all-wheel-drive electric wheel vehicle, and the all-wheel-drive electric wheel vehicle is a pure electric vehicle with all wheels driven by wheel hub motors directly; the estimation method comprises the following steps: effective wheel screening, longitudinal acceleration signal preprocessing and longitudinal vehicle speed estimation; the system comprises an effective wheel screening module, a longitudinal acceleration signal preprocessing module and a longitudinal vehicle speed estimation module. The invention considers the wheel motion state and the validity of the rotating speed information thereof, fuses the longitudinal acceleration information and realizes the estimation of the longitudinal speed of the vehicle; the method provided by the invention weakens the dependence on the precision of the dynamic model, and has strong real-time performance and high performability.

Description

longitudinal speed estimation method and system for all-wheel-drive electric wheel automobile
Technical Field
the invention belongs to the field of vehicle dynamics control, and particularly relates to a longitudinal vehicle speed estimation method and system for an all-wheel-drive electric wheel vehicle.
Background
with the increasing contradiction between the traditional energy and the environmental problems, the full-drive electric wheel automobile gradually becomes a research focus and a hot spot in the last decade. The full-drive electric wheel automobile is a type of electric automobile which directly drives to run by adopting a motor arranged inside a wheel hub (wheel edge) as a power source. The full-drive electric wheel automobile cancels a traditional transmission mechanism, and simplifies the spatial arrangement of a vehicle chassis, thereby being more energy-saving and safer. Meanwhile, the full-drive electric wheel automobile can independently distribute the torque of the driving wheels, and compared with the traditional fuel oil automobile and a centralized driving electric automobile, the decoupling of a power source is realized, so that the dynamic control freedom degree is increased, and the improvement of the power performance of the electric automobile is facilitated.
vehicle longitudinal speed information is an important parameter for a dynamic-related electronic control system. The electric wheel automobile driven by the four-wheel hub does not have the rotating speed of the driven wheel as a reference, so that the difficulty of estimating the speed of the automobile is increased. Meanwhile, due to the working principle of the inertial sensor, the component of centripetal acceleration is coupled in the acquired longitudinal acceleration signal, interference noise is superimposed, accurate longitudinal vehicle running acceleration information cannot be directly obtained, and a related dynamics control algorithm is influenced.
In the existing method for estimating the longitudinal speed of the all-drive electric wheel automobile, acceleration information is partially adopted to directly perform integration, and errors of an estimation result are overlarge due to the fact that errors are accumulated by integration along with the time; and the other part is established based on a longitudinal dynamic model, and the estimation effect mostly depends on the precision of the dynamic model or the requirement of acquiring the tire force of the wheel. However, the complex dynamic model is difficult to be applied in the practical process, and finally, the longitudinal speed information of the vehicle is difficult to be effectively acquired.
disclosure of Invention
the invention aims to overcome the defects of the prior art and provides a longitudinal speed estimation method and system for a full-drive electric wheel automobile. The full-drive electric wheel automobile is a pure electric vehicle with all wheels directly driven to run by adopting the motors arranged inside (wheel edges) of the wheel hubs of the wheels of the automobile.
in order to realize the purpose of the invention, the following technical scheme is adopted:
the invention provides a longitudinal speed estimation method for a full-drive electric wheel automobile, wherein the full-drive electric wheel automobile is provided with n wheels, and each wheel is directly driven by a hub motor; the method is characterized by comprising the following steps:
1) efficient wheel screening
1.1) calculating the slip ratio of each wheel according to the wheel rotating speed of the current moment and the longitudinal vehicle speed estimated value of the previous moment fed back by each hub motor, wherein the slip ratio is shown as the formula (1):
wherein Si represents a slip ratio of the i-th wheel; vxp, the longitudinal vehicle speed estimated value at the last moment; vwi represents the equivalent speed of the ith wheel at the current moment, and is obtained by calculating the real-time rotating speed of the corresponding hub motor and the rolling radius of the wheel, as shown in formula (2):
in the formula, ni represents the real-time rotating speed of a hub motor for driving the ith wheel; ri represents the rolling radius of the i-th wheel;
Setting the initial values of the longitudinal vehicle speed value Vxp, the equivalent speed Vwi of the wheel and the slip ratio Si of the wheel to be 0;
1.2) obtaining the slip state of the wheel according to the slip rate of the wheel, wherein the slip state is used as a judgment criterion of the wheel rotating speed effectiveness, and the calculation of the wheel slip state is shown as a formula (3):
where Msi represents a slip state of the ith wheel; sth represents a threshold value of the wheel slip rate, and the experience value is 0.15-0.2 according to the mechanical characteristics of the tire; when the slip ratio Si of the ith wheel is less than or equal to the slip ratio threshold value Sth of the wheel, judging that the ith wheel does not slip, and when Msi is 1, namely the ith wheel is an effective wheel, the rotating speed information of the wheel is effective; when the slip rate Si of the ith wheel is greater than the slip rate threshold value Sth of the wheel, the ith wheel is considered to slip, and Msi is 0, and the rotating speed information of the wheel is invalid;
1.3) forming the rotating speeds of all effective wheels into an effective wheel rotating speed vector, wherein the formula (4) is as follows:
in the formula, ne represents an effective wheel rotating speed vector, and the number of elements contained in ne is the number N of effective wheels; represents the effective rotating speed of the wheel, and is represented by the formula (5):
2) longitudinal acceleration pre-processing
2.1) calculating the longitudinal acceleration of the vehicle according to the longitudinal acceleration, the transverse acceleration and the yaw velocity of the vehicle measured by the inertial sensor, wherein the formula (6) is as follows:
in the formula, the vehicle longitudinal acceleration at the current moment is represented; ax represents the projection value of the absolute acceleration of the vehicle at the current moment in the longitudinal direction of the vehicle coordinate system, and gamma represents the yaw velocity at the current moment, which are measured by an inertial sensor; vy represents a vehicle transverse speed value at the current moment, and is calculated by summing vehicle transverse acceleration, as shown in formula (7):
in the formula, t0 represents an initial time; t represents the current time; Δ t represents a sampling interval; represents the vehicle lateral acceleration at the present moment, as shown in equation (8):
In the formula, ay represents a projection value of the absolute acceleration of the vehicle at the current moment in the transverse direction of the vehicle coordinate system, and is measured by an inertial sensor;
2.2) eliminating the noise interference in the signal measurement by the longitudinal acceleration of the vehicle at the current moment obtained in the step 2.1) through a filter function to obtain a filter value of the longitudinal acceleration of the vehicle at the current moment, as shown in the formula (9):
Wherein, the vehicle longitudinal acceleration filtering value is represented; filter represents a general Filter function;
3) longitudinal vehicle speed estimation:
According to the number of effective wheels at the current moment, fusing a vehicle longitudinal acceleration filter value at the current moment, and calculating a vehicle longitudinal speed estimation value at the current moment, as shown in formula (10):
in the formula, Vx represents the longitudinal vehicle speed estimated value of the vehicle at the current moment; when the number of the effective wheels is not equal to zero, calculating to obtain a longitudinal vehicle speed estimated value at the current moment through the average value of the rotating speeds of the effective wheels; when the number of the effective wheels is equal to zero, namely all the wheels enter a slip state, the longitudinal speed estimated value at the current moment is obtained by summing the longitudinal acceleration filtering values of the vehicles, the initial value of the summation is the longitudinal speed estimated value at the last moment when all the wheels are failed, and the summation finishing moment is the current moment t.
the invention also provides a longitudinal speed estimation system for the all-wheel-drive electric wheel automobile, wherein the all-wheel-drive electric wheel automobile is provided with n wheels, and each wheel is directly driven by one hub motor; the system is characterized by comprising a memory and a processor, wherein the processor is internally provided with an effective wheel screening module, a longitudinal acceleration signal preprocessing module and a longitudinal vehicle speed estimation module;
the effective wheel screening module is used for selecting wheels without sliding tendency to participate in longitudinal vehicle speed estimation, and executes the following steps:
1.1) calculating the slip ratio of each wheel according to the wheel rotating speed of the current moment and the longitudinal vehicle speed estimated value of the previous moment fed back by each hub motor, wherein the slip ratio is shown as the formula (1):
wherein Si represents a slip ratio of the i-th wheel; vxp, the longitudinal vehicle speed estimated value at the last moment; vwi represents the equivalent speed of the ith wheel at the current moment, and is obtained by calculating the real-time rotating speed of the corresponding hub motor and the rolling radius of the wheel, as shown in formula (2):
in the formula, ni represents the real-time rotating speed of a hub motor for driving the ith wheel; ri represents the rolling radius of the i-th wheel;
Setting the initial values of the longitudinal vehicle speed value Vxp, the equivalent speed Vwi of the wheel and the slip ratio Si of the wheel to be 0;
1.2) obtaining the slip state of the wheel according to the slip rate of the wheel, wherein the slip state is used as a judgment criterion of the wheel rotating speed effectiveness, and the calculation of the wheel slip state is shown as a formula (3):
where Msi represents a slip state of the ith wheel; sth represents a threshold value of the wheel slip rate, and the experience value is 0.15-0.2 according to the mechanical characteristics of the tire; when the slip ratio Si of the ith wheel is less than or equal to the slip ratio threshold value Sth of the wheel, judging that the ith wheel does not slip, and when Msi is 1, namely the ith wheel is an effective wheel, the rotating speed information of the wheel is effective; when the slip rate Si of the ith wheel is greater than the slip rate threshold value Sth of the wheel, the ith wheel is considered to slip, and Msi is 0, and the rotating speed information of the wheel is invalid;
1.3) forming the rotating speeds of all effective wheels into an effective wheel rotating speed vector, wherein the formula (4) is as follows:
in the formula, ne represents an effective wheel rotating speed vector, and the number of elements contained in ne is the number N of effective wheels; represents the effective rotating speed of the wheel, and is represented by the formula (5):
the longitudinal acceleration signal preprocessing module is used for acquiring a vehicle longitudinal acceleration signal and filtering the vehicle longitudinal acceleration signal, and executes the following steps:
2.1) calculating the longitudinal acceleration of the vehicle according to the longitudinal acceleration, the transverse acceleration and the yaw velocity of the vehicle measured by the inertial sensor, wherein the formula (6) is as follows:
in the formula, the vehicle longitudinal acceleration at the current moment is represented; ax represents the projection value of the absolute acceleration of the vehicle at the current moment in the longitudinal direction of the vehicle coordinate system, and gamma represents the yaw velocity at the current moment, which are measured by an inertial sensor; vy represents a vehicle transverse speed value at the current moment, and is calculated by summing vehicle transverse acceleration, as shown in formula (7):
in the formula, t0 represents an initial time; t represents the current time; Δ t represents a sampling interval; represents the vehicle lateral acceleration at the present time, as shown in equation (8):
In the formula, ay represents a projection value of the absolute acceleration of the vehicle at the current moment in the transverse direction of the vehicle coordinate system, and is measured by an inertial sensor;
2.2) eliminating the noise interference in the signal measurement by the longitudinal acceleration of the vehicle at the current moment obtained in the step 2.1) through a filter function to obtain a filter value of the longitudinal acceleration of the vehicle at the current moment, as shown in the formula (9):
wherein, the vehicle longitudinal acceleration filtering value is represented; filter represents a general Filter function;
the longitudinal vehicle speed estimation module fuses effective wheel rotating speed information and longitudinal acceleration information to obtain longitudinal vehicle speed, and executes the following steps:
According to the number of effective wheels at the current moment, fusing a vehicle longitudinal acceleration filter value at the current moment, and calculating a vehicle longitudinal speed estimation value at the current moment, as shown in formula (10):
in the formula, Vx represents the longitudinal vehicle speed estimated value of the vehicle at the current moment; when the number of the effective wheels is not equal to zero, calculating to obtain a longitudinal vehicle speed estimated value at the current moment through the average value of the rotating speeds of the effective wheels; when the number of the effective wheels is equal to zero, namely all the wheels enter a slip state, the longitudinal speed estimated value at the current moment is obtained by summing the longitudinal acceleration filtering values of the vehicles, the initial value of the summation is the longitudinal speed estimated value at the last moment when all the wheels are failed, and the summation finishing moment is the current moment t.
The invention has the characteristics and beneficial effects that:
1. the method and the system for estimating the longitudinal speed of the all-wheel-drive electric wheel automobile fully utilize the rotation speed information of the wheels, consider the motion state of the wheels, use the rotation speed information as a judgment basis for the effectiveness of the rotation speed, and fuse the measurement information of the inertial sensor, thereby effectively exerting the redundancy characteristic of an actuating mechanism of the electric wheel automobile and having strong feasibility;
2. The method and the system for estimating the longitudinal speed of the all-drive electric wheel automobile weaken the dependence on the precision of a dynamic model, do not need to acquire state information such as tire force in advance, reduce the accumulated error of acceleration integration, and have the advantages of high estimation precision, small data calculation amount and high calculation speed.
3. the longitudinal speed estimation method and system for the full-drive electric wheel automobile can be expanded to a multi-shaft full-drive electric wheel automobile with the same hardware structure.
drawings
FIG. 1 is a block flow diagram of a longitudinal vehicle speed estimation method of the present invention.
Detailed Description
the technical scheme of the invention is further explained by combining the drawings and the specific embodiment as follows:
the longitudinal speed estimation method of the full-drive electric wheel automobile is used for an electric automobile driven by 4 hub motors, each hub motor directly drives a wheel, and a flow chart is shown in figure 1. The method specifically comprises the following steps:
1) the effective wheel screening comprises the following specific steps:
1.1) calculating the slip ratio of each wheel according to the wheel rotating speed of the current moment and the longitudinal vehicle speed estimated value of the previous moment fed back by each hub (wheel side) motor, wherein the slip ratio is shown as the formula (1):
in the formula, the lower subscript i is 1, 2, 3, 4, which corresponds to the front left, front right, rear left and rear right wheels in sequence; si represents the slip ratio of the ith wheel; vxp, the longitudinal vehicle speed estimated value at the last moment is a scalar quantity defined in the vehicle coordinate system; vwi represents the equivalent speed of the ith wheel at the current moment, and is obtained by calculating the real-time rotating speed of the corresponding hub motor and the rolling radius of the wheel, as shown in formula (2):
In the formula, ni represents the real-time rotating speed of a hub motor for driving the ith wheel; ri represents the rolling radius of the ith wheel, and the rolling radii of the wheels are all equal in the embodiment; the initial values of the longitudinal vehicle speed estimated value Vxp, the equivalent speed Vwi of the wheel and the slip ratio Si of the wheel are all 0;
1.2) obtaining the slip state of the wheel according to the slip rate of the wheel, and using the slip state as a judgment criterion of the wheel rotating speed effectiveness. The wheel slip condition is calculated as shown in equation (3):
where Msi represents a slip state of the ith wheel; sth represents a threshold value of the wheel slip rate, and the threshold value is set according to the mechanical characteristics of the tire, and the experience value is 0.15-0.2; when the slip ratio Si of the ith wheel is less than or equal to the slip ratio threshold value Sth of the wheel, judging that the ith wheel does not slip, and when Msi is 1, namely the ith wheel is an effective wheel, the rotating speed information of the wheel is effective; when the slip rate Si of the ith wheel is greater than the slip rate threshold value Sth of the wheel, the ith wheel is considered to slip, and Msi is 0, and the rotating speed information of the wheel is invalid;
1.3) forming the rotating speeds of all effective wheels into an effective wheel rotating speed vector, wherein the formula (4) is as follows:
in the formula, ne represents an effective wheel rotating speed vector, and the number of elements contained in ne is the number N of effective wheels; represents the effective rotating speed of the wheel, and is represented by the formula (5):
2) longitudinal acceleration preprocessing, which comprises the following steps:
2.1) calculating the longitudinal acceleration of the vehicle according to the longitudinal acceleration, the transverse acceleration and the yaw velocity of the vehicle measured by the inertial sensor, wherein the formula (6) is as follows:
in the formula, the vehicle longitudinal acceleration at the current moment is represented; ax represents the projection value of the absolute acceleration of the vehicle at the current moment in the longitudinal direction of the vehicle coordinate system, and gamma represents the yaw velocity at the current moment, which are measured by an inertial sensor; vy represents a vehicle transverse speed value at the current moment, and is calculated by summing vehicle transverse acceleration, as shown in formula (7):
in the formula, t0 represents an initial time; t represents the current time; Δ t represents the sampling interval, which depends on the data acquisition accuracy of the sensor, which is 50ms in this example; represents the vehicle lateral acceleration at the present moment, as shown in equation (8):
In the formula, ay represents a projection value of the absolute acceleration of the vehicle at the current moment in the transverse direction of the vehicle coordinate system, and is measured by an inertial sensor;
2.2) eliminating the noise interference in the signal measurement by the longitudinal acceleration of the vehicle at the current moment obtained in the step 2.1) through a filter function to obtain a filter value of the longitudinal acceleration of the vehicle at the current moment, as shown in the formula (9):
wherein, the vehicle longitudinal acceleration filtering value is represented; filter represents a general Filter function, such as a Kalman Filter function;
3) longitudinal vehicle speed estimation comprises the following specific steps:
according to the number of effective wheels at the current moment, fusing a vehicle longitudinal acceleration filter value at the current moment, and calculating a vehicle longitudinal speed estimation value at the current moment, as shown in formula (10):
in the formula, Vx represents the longitudinal vehicle speed estimated value of the vehicle at the current moment; when the number of the effective wheels is not equal to zero, calculating to obtain a longitudinal vehicle speed estimated value at the current moment through the average value of the rotating speeds of the effective wheels; when the number of the effective wheels is equal to zero, namely all the wheels enter a slip state, the longitudinal speed estimated value at the current moment is obtained by summing the longitudinal acceleration filtering values of the vehicles, the initial value of the summation is the longitudinal speed estimated value at the last moment when all the wheels are failed, and the summation finishing moment is the current moment t.
when the method is applied, the method is integrated and solidified in a processor through the conventional programming technology in the field, a longitudinal speed estimation system for the full-drive electric wheel automobile is formed through the processor and a memory, and an effective wheel screening module, a longitudinal acceleration signal preprocessing module and a longitudinal speed estimation module are arranged in the processor; the effective wheel screening module is used for selecting wheels without sliding tendency to participate in longitudinal vehicle speed estimation, and the specific execution process refers to the step 1); the longitudinal acceleration signal preprocessing module is used for acquiring a longitudinal acceleration signal of the vehicle and filtering the longitudinal acceleration signal, and the specific execution process refers to the step 2); and the longitudinal vehicle speed estimation module fuses effective wheel rotating speed information and longitudinal acceleration information to obtain longitudinal vehicle speed, and the specific execution process refers to the step 3).
although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (2)

1. a longitudinal speed estimation method for a full-drive electric wheel automobile is provided, wherein the full-drive electric wheel automobile is provided with n wheels, and each wheel is directly driven by a hub motor; the method is characterized by comprising the following steps:
1) efficient wheel screening
1.1) calculating the slip ratio of each wheel according to the wheel rotating speed of the current moment and the longitudinal vehicle speed estimated value of the previous moment fed back by each hub motor, wherein the slip ratio is shown as the formula (1):
wherein Si represents a slip ratio of the i-th wheel; vxp, the longitudinal vehicle speed estimated value at the last moment; vwi represents the equivalent speed of the ith wheel at the current moment, and is obtained by calculating the real-time rotating speed of the corresponding hub motor and the rolling radius of the wheel, as shown in formula (2):
in the formula, ni represents the real-time rotating speed of a hub motor for driving the ith wheel; ri represents the rolling radius of the i-th wheel;
setting the initial values of the longitudinal vehicle speed value Vxp, the equivalent speed Vwi of the wheel and the slip ratio Si of the wheel to be 0;
1.2) obtaining the slip state of the wheel according to the slip rate of the wheel, wherein the slip state is used as a judgment criterion of the wheel rotating speed effectiveness, and the calculation of the wheel slip state is shown as a formula (3):
where Msi represents a slip state of the ith wheel; sth represents a threshold value of the wheel slip rate, and the experience value is 0.15-0.2 according to the mechanical characteristics of the tire; when the slip ratio Si of the ith wheel is less than or equal to the slip ratio threshold value Sth of the wheel, judging that the ith wheel does not slip, and when Msi is 1, namely the ith wheel is an effective wheel, the rotating speed information of the wheel is effective; when the slip rate Si of the ith wheel is greater than the slip rate threshold value Sth of the wheel, the ith wheel is considered to slip, and Msi is 0, and the rotating speed information of the wheel is invalid;
1.3) forming the rotating speeds of all effective wheels into an effective wheel rotating speed vector, wherein the formula (4) is as follows:
in the formula, ne represents an effective wheel rotating speed vector, and the number of elements contained in ne is the number N of effective wheels; represents the effective rotating speed of the wheel, and is represented by the formula (5):
2) Longitudinal acceleration pre-processing
2.1) calculating the longitudinal acceleration of the vehicle according to the longitudinal acceleration, the transverse acceleration and the yaw velocity of the vehicle measured by the inertial sensor, wherein the formula (6) is as follows:
in the formula, the vehicle longitudinal acceleration at the current moment is represented; ax represents the projection value of the absolute acceleration of the vehicle at the current moment in the longitudinal direction of the vehicle coordinate system, and gamma represents the yaw velocity at the current moment, which are measured by an inertial sensor; vy represents a vehicle transverse speed value at the current moment, and is calculated by summing vehicle transverse acceleration, as shown in formula (7):
in the formula, t0 represents an initial time; t represents the current time; Δ t represents a sampling interval; represents the vehicle lateral acceleration at the present moment, as shown in equation (8):
In the formula, ay represents a projection value of the absolute acceleration of the vehicle at the current moment in the transverse direction of the vehicle coordinate system, and is measured by an inertial sensor;
2.2) eliminating the noise interference in the signal measurement by the longitudinal acceleration of the vehicle at the current moment obtained in the step 2.1) through a filter function to obtain a filter value of the longitudinal acceleration of the vehicle at the current moment, as shown in the formula (9):
wherein, the vehicle longitudinal acceleration filtering value is represented; filter represents a general Filter function;
3) longitudinal vehicle speed estimation:
according to the number of effective wheels at the current moment, fusing a vehicle longitudinal acceleration filter value at the current moment, and calculating a vehicle longitudinal speed estimation value at the current moment, as shown in formula (10):
in the formula, Vx represents the longitudinal vehicle speed estimated value of the vehicle at the current moment; when the number of the effective wheels is not equal to zero, calculating to obtain a longitudinal vehicle speed estimated value at the current moment through the average value of the rotating speeds of the effective wheels; when the number of the effective wheels is equal to zero, namely all the wheels enter a slip state, the longitudinal speed estimated value at the current moment is obtained by summing the longitudinal acceleration filtering values of the vehicles, the initial value of the summation is the longitudinal speed estimated value at the last moment when all the wheels are failed, and the summation finishing moment is the current moment t.
2. A longitudinal speed estimation system for a full-drive electric wheel automobile is provided, wherein the full-drive electric wheel automobile is provided with n wheels, and each wheel is directly driven by a hub motor; the system is characterized by comprising a memory and a processor, wherein the processor is internally provided with an effective wheel screening module, a longitudinal acceleration signal preprocessing module and a longitudinal vehicle speed estimation module;
the effective wheel screening module is used for selecting wheels without sliding tendency to participate in longitudinal vehicle speed estimation, and executes the following steps:
1.1) calculating the slip ratio of each wheel according to the wheel rotating speed of the current moment and the longitudinal vehicle speed estimated value of the previous moment fed back by each hub motor, wherein the slip ratio is shown as the formula (1):
wherein Si represents a slip ratio of the i-th wheel; vxp, the longitudinal vehicle speed estimated value at the last moment; vwi represents the equivalent speed of the ith wheel at the current moment, and is obtained by calculating the real-time rotating speed of the corresponding hub motor and the rolling radius of the wheel, as shown in formula (2):
In the formula, ni represents the real-time rotating speed of a hub motor for driving the ith wheel; ri represents the rolling radius of the i-th wheel;
setting the initial values of the longitudinal vehicle speed value Vxp, the equivalent speed Vwi of the wheel and the slip ratio Si of the wheel to be 0;
1.2) obtaining the slip state of the wheel according to the slip rate of the wheel, wherein the slip state is used as a judgment criterion of the wheel rotating speed effectiveness, and the calculation of the wheel slip state is shown as a formula (3):
where Msi represents a slip state of the ith wheel; sth represents a threshold value of the wheel slip rate, and the experience value is 0.15-0.2 according to the mechanical characteristics of the tire; when the slip ratio Si of the ith wheel is less than or equal to the slip ratio threshold value Sth of the wheel, judging that the ith wheel does not slip, and when Msi is 1, namely the ith wheel is an effective wheel, the rotating speed information of the wheel is effective; when the slip rate Si of the ith wheel is greater than the slip rate threshold value Sth of the wheel, the ith wheel is considered to slip, and Msi is 0, and the rotating speed information of the wheel is invalid;
1.3) forming the rotating speeds of all effective wheels into an effective wheel rotating speed vector, wherein the formula (4) is as follows:
In the formula, ne represents an effective wheel rotating speed vector, and the number of elements contained in ne is the number N of effective wheels; represents the effective rotating speed of the wheel, and is represented by the formula (5):
the longitudinal acceleration signal preprocessing module is used for acquiring a vehicle longitudinal acceleration signal and filtering the vehicle longitudinal acceleration signal, and executes the following steps:
2.1) calculating the longitudinal acceleration of the vehicle according to the longitudinal acceleration, the transverse acceleration and the yaw velocity of the vehicle measured by the inertial sensor, wherein the formula (6) is as follows:
in the formula, the vehicle longitudinal acceleration at the current moment is represented; ax represents the projection value of the absolute acceleration of the vehicle at the current moment in the longitudinal direction of the vehicle coordinate system, and gamma represents the yaw velocity at the current moment, which are measured by an inertial sensor; vy represents a vehicle transverse speed value at the current moment, and is calculated by summing vehicle transverse acceleration, as shown in formula (7):
in the formula, t0 represents an initial time; t represents the current time; Δ t represents a sampling interval; represents the vehicle lateral acceleration at the present moment, as shown in equation (8):
in the formula, ay represents a projection value of the absolute acceleration of the vehicle at the current moment in the transverse direction of the vehicle coordinate system, and is measured by an inertial sensor;
2.2) eliminating the noise interference in the signal measurement by the longitudinal acceleration of the vehicle at the current moment obtained in the step 2.1) through a filter function to obtain a filter value of the longitudinal acceleration of the vehicle at the current moment, as shown in the formula (9):
wherein, the vehicle longitudinal acceleration filtering value is represented; filter represents a general Filter function;
the longitudinal vehicle speed estimation module fuses effective wheel rotating speed information and longitudinal acceleration information to obtain longitudinal vehicle speed, and executes the following steps:
according to the number of effective wheels at the current moment, fusing a vehicle longitudinal acceleration filter value at the current moment, and calculating a vehicle longitudinal speed estimation value at the current moment, as shown in formula (10):
In the formula, Vx represents the longitudinal vehicle speed estimated value of the vehicle at the current moment; when the number of the effective wheels is not equal to zero, calculating to obtain a longitudinal vehicle speed estimated value at the current moment through the average value of the rotating speeds of the effective wheels; when the number of the effective wheels is equal to zero, namely all the wheels enter a slip state, the longitudinal speed estimated value at the current moment is obtained by summing the longitudinal acceleration filtering values of the vehicles, the initial value of the summation is the longitudinal speed estimated value at the last moment when all the wheels are failed, and the summation finishing moment is the current moment t.
CN201910721634.9A 2019-08-06 2019-08-06 Longitudinal speed estimation method and system for all-wheel-drive electric wheel automobile Pending CN110539646A (en)

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Application publication date: 20191206